Ablative skin resurfacing has been performed using carbon dioxide lasers emitting radiation at 10.6 microns. (See for example, U.S. Pat. No. 5,335,242). While these lasers could provide good results, recovery times were long. The long recovery times have been attributed to the significant depth of thermal damage associated with this longer wavelength radiation.
In an effort to reduce recovery time, Er:YAG lasers, operating at an output wavelength of 2.94 μm, have been used to ablate tissue. The very high water absorption associated with the 2.94 μm wavelength decreased thermal damage and decreased recovery times, although a reduction in efficacy was sometimes observed. Generally, this reduction in efficacy is thought to be a consequence of a reduced thermal damage profile in skin, post-ablation. An example of the use of Er:YAG lasers for tissue treatment can be found in U.S. Pat. No. 6,395,000 which utilizes high repetition rate pulses (greater than 100 hertz). Another approach is to treat the tissue with micropulses within a relatively long pulse envelope. See U.S. Patent Applications 2001/0016732 and 2004/0133190. See also U.S. Pat. No. 6,193,711. All of these patent documents are incorporated by reference. The approach described herein is intended to both increase efficacy and reduce recovery time.